With the advent of combination therapy for individuals living with HIV, the issue of adherence to medication has become increasingly salient. Not only does poor adherence to medication negatively effect the patient's prognosis, but concerns are rising about the threat of mufti-drug resistant strains of HIV and their impact on public health. As the numbers of adolescents and young adults with HIV continue to increase, it becomes important to investigate medication adherence within a group with historically low rates of adherence. This research project aims to expand the existing HIV adherence literature by exploring the relationships between cognitive functioning, negative affective states, and medication adherence in HIV-infected youth. A cross-sectional study design will be used to investigate these predictor variables as well as the modifying effects of medical status and substance use. Adolescents and young adults infected with HIV will be recruited from a publicly-funded medical facility to participate in an interview. In addition to expanding the existing literature in this area, the results from this project will be important in the development and implementation of interventions aimed at increasing medication adherence within an at-risk population.